Metering pump



p 1966 P. E. CURRY ETAL 3,272,141

METERING PUMP Filed May 13, 1964 INVENTOR. PHIL/P E. CURRY PA QIAYOTIS I? DEMOPOULOS ATT NEY United States Patent 3,272,141 METERING PUMP Philip E. Curry and Panayotis P. Demopoulos, Pensacola, Fla., assignors to Monsanto Company, St. Louis, Mo., a corporation of Delaware Filed May 13, 1964, Ser. No. 367,071 2 Claims. (Cl. 103126) This invention relates to a positive displacement metering pump with a metered output stream which is substantially free of pulsations.

A well known prior art positive displacement metering pump is formed by driven meshing gears in a closely fitting housing. As normally constructed, such pumps produce an output stream which has substantial pulsations or variations in instantaneous flow as the individual teeth mesh. According to the present invention, such pulsations are markedly reduced and a more constant flow is achieved.

A primary object of the invention is to provide a positive displacement gear pump with a substantially constantflow output stream. A futher object is to provide for combining a plurality of pulsating output streams so phased as to substantially cancel the pulsations. A further object is to provide a pump construction incorporating the equivalent of two or more pumps, which construction may be readily employed in existing pumps with a minimum of alteration.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the constructions hereinafter set forth, and the scope of the invention will be indicated in the claims.

For a more complete understanding of the nature and objects of the invent-ion, reference should be made to the following detailed description taken in connection with the accompanying drawing, in which:

FIGURE 1 is a plan view, partly broken away, of a preferred embodiment of the present invention;

FIGURE 2. is a sectional view taken along line 22 of FIGURE 1.

Referring now generally to FIGURE 1, there is illustrated a pump housing 18 having a recess 20 comprising central chamber 22 and end chambers 24 and 26, each of which communicates with chamber 22. A central impeller or gear 28 is supported on and preferably is driven by shaft 30 within the central chamber 22. A first idler gear 32 is mounted on shaft 34 within first end chamber 24, and similarly second idler gear 36 is mounted on shaft 38 within the second end chamber 26. Gears 32 and 36 are each meshed with and driven by central gear 28 in the preferred embodiment of the invention, although any or all of the gears may be driven. The bottom surface 40 of recess 20, together with top plate 42 which is bolted to housing 18, enclose the several chambers.

Ports 44 and 46 are located in housing 18 on opposite sides of the region where gears 28 and 32 mesh, and ports 48 and 50- are similarly located on opposite sides of the region where gears 28 and 36 mesh. The side walls of housing 1-8 defining recess 20 closely conform to the path of the gear-tooth tips except in the vicinities of the various ports, in order to provide effective sealing, as will be readily understood by those skilled in the art. This con- Patented Sept. 13, 1966 struction provides in effect two pump sections with central gear 28 shared by both sections. When the gears rotate in the directions illustrated in FIGURE 1, fluid supplied to inlet ports 44 and 50 will be discharged through outlet ports 46 and 48. As illustrated in FIGURE 2, ports 46 and 48 are connected to a common output passageway 52 by a gallery 54 so that a single output stream is provided by the pump assembly. A similar gallery may connect inlet ports 44 and 50 if desired.

Referring again to FIGURE 1, the axes of gears 28 and 32 are parallel with one another and define a plane which is normal to the drawing and which intersects the drawing along the line 56. Similarly, the axes of gears 28 and 36 define a second plane perpendicular to the drawing, and which intersects the drawing along line 58. According to the present invention, the offset angle 0 formed by lines 56 and 58 is selected to be equal to (/n)(4K+1), where n is the number of teeth on gear 28 and K is an integer (which may include zero as well as positive or negative values), in order to minimize the inherent pulsations in flow produced by intermeshing of the teeth on the several gears. When angle 0 is selected according to the above formula, inherent pulsations in flow are reduced by approximately a factor of 10 as compared to the output if all three axes were in the same plane (6 equals 0). This produces a much more constant and continuous flow in output passage 52 without any sacrifice in the positiveness of displacement. In the specific embodiment illustrated in FIGURE 1, n equals six, while K has been selected to equal zero; accordingly 0 equals 15".

It should be noted that the pump is shown with three identical gears only for purposes of illustration: The gears need not be of the same diameter, nor need they have the same number of teeth. Six-toothed gears were selected for illustration so that 6' would be large enough to be readily apparent in the drawing. In practice, a considerably greater number of teeth will usually be provided, and the gear teeth would normally be constructed in the form of conventional spur gear teeth.

It may be seen from the above description and the accompanying drawing that pump constructions according to the present invention produce positive-displacement metering pumps having substantially constant flow output streams, by alignment of the gear axes according to the cited formula. With the exception of this change, the ordinary principles of positive-displacement pump construction may be employed, insofar as concerns materials, clearances, etc.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Having described our invention, what we claim as new and desire to secure by Letters Patent is:

1. Pumping apparatus for producing a substantially constant flow comprising in combination:

(a) a pump housing, and

(b) meshed gears within said housing, said meshed gears consisting of a central spur gear and first and second further spur gears, each of said further gears meshing with said central gear to form respectively first and second meshed regions,

degrees, when n equals the number of teeth on the central gear and K equals an integer, each of said gears being a spur gear,

(d) and said housing forming with said gears a positive displacement pump with a single output stream.

2. The pumping apparatus defined in claim 1, wherein said housing means comprises:

(a) first, second, third and fourth ports in said housing spaced about said central gear in that order in the direction in which said central gear rotates;

(:b) said first and said second ports being positioned on opposite sides of said first meshed region;

(c) said third and fourth ports being positioned on opposite sides of said second meshed region;

((1) means for supplying fluid to said second and said fourth ports;

(e) and means for combining the output flow of said first and said third ports.

References Cited by the Examiner UNITED STATES PATENTS 1,363,793 12/1920 Kirkham 103-426 2,159,748 5/1939 Miller et al. 230-141 2,699,122 1/1955 Erickson 103-126 FOREIGN PATENTS 1,103,716 6/1955 France.

15 MARK NEWMAN, Primary Examiner.

WILBUR J. GOODLIN, Examiner. 

1. PUMPING APPARATUS FOR PRODUCING A SUBSTANTIALLY CONSTANT FLOW COMPRISING IN COMBINATION: (A) A PUMP HOUSING, AND (B) MESHED GEARS WITHIN SAID HOUSING, SAID MESHED GEARS CONSISTING OF A CENTRAL SPUR GEAR AND FIRST AND SECOND FURTHER SPUR GEARS, EACH OF SAID FURTHER GEARS MESHING WITH SAID CENTRAL GEAR TO FORM RESPECTIVELY FIRST AND SECOND MESHED REGIONS, (C) A THREE-GEAR POSITIVELY DISPLACEMENT PUMP WHEREIN THE OFFSET ANGLE DEFINED BY THE GEARS EQUALS 